mingw-gcc 8.1.0 in rawhide

Hi, Just a quick heads up that I've updated mingw-gcc to 8.1.0 and the mingw-w64 toolchain to 5.0.4 in preparation of the rawhide mass rebuild this week. F28 is already on gcc 8, so if any mingw package should fail to build with the new compiler, it should mostly be just the matter to hunting down relevant fixes in the native packages and porting them to the mingw packages. mingw-binutils is also new (2.30), thanks Sandro for taking care of that! Kalev